Natural bone composition may be simulated by scaffolds for bone tissue engineering composed of collagen/HA composites. To fabricate a collagen/HA composite, a conventional method may utilize standing mineral solutions that contain supersaturated calcium-phosphate ions to presoak a porous collagen scaffold. However, high calcium-phosphate ion concentrations typically cause the minerals to precipitate out of solution rather than only crystallizing on the collagen scaffold. As a result, the mineral content is deposited on the surface of the collagen fibers rather than within them, which often obstruct the pores of the collagen scaffold.
Another common preparation method premixes collagen and synthetic HA nanoparticles to form collagen-apatite slurry. This mixing technique mechanically blends collagen and HA to form a physical mixture that lacks any chemical bonding. In addition, synthetic HA nanoparticles are often different in crystal size and crystalline phase from the hydroxyapatite found in natural bone. As a result, the collagen/HA composites that are fabricated using this technique are understood to possess poor mechanical properties with diminished osteoconductive and osteoinductive properties.
These conventional in vitro collagen mineralization methods are different from the in vivo bone formation process, and often result in scaffolds that are generally unsuitable for bone tissue engineering.